from c:/deepdive/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require' from c:/deepdive/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require' from ./../unittests/setup.rb:21 from c:/deepdive/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require' from c:/deepdive/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require' from core_tests.rb:8

Googled for "klass': uninitialized constant Watir::IE" and found email from Bret that said to add "require 'watir/ie" to core_tests.rb, so I did and it started to work.